Enterohemorrhagic Escherichia coli contaminated foods are a major cause of infection outbreaks with serious consequences. One of the largest outbreaks occurred in Japan in 1996, where over 10,000 people were infected and 11 died. Current detection methods for pathogenic bacteria such as E. coil rely on bacterial recognition using fluorescently labeled antibodies, DNA probes, or bacteriophages. While fluorescent conjugated polymers have found use in a variety of biological sensing applications, such as recognition of proteins by electrostatic interactions and detection of pathogens by DNA hybridization, the inventors know of no reported detection schemes for cells.
In many cases, pathogens bind to surface carbohydrates displayed on the cells they infect. A series of carbohydrate-pathogen interactions has been described, for example, E. coli binds to mannose, influenza virus binds to sialic acid, etc. The interactions of pathogens with cell surface carbohydrates are often multivalent, which results in higher binding affinity compared to monovalent binding.